There is known an adhesive tape in which a glass cloth impregnated with a fluorine resin is used as a substrate and in which an adhesive agent layer is provided on one surface of the substrate (for example, Patent Literature 1). This adhesive tape exhibits high heat resistance derived from the glass cloth and the fluorine resin, and the other surface on which no adhesive agent layer is formed exhibits excellent properties derived from the fluorine resin, such as high releasability and slipperiness; therefore, this adhesive tape is used in various applications. One of the applications is coating of a heat sealing part of a heat sealer. This coating prevents a to-be-heat-sealed object from being fused with the heat sealing part.
A glass cloth is a woven fabric obtained by weaving glass yarns as the warp and weft. In general, glass yarns used as the warp and weft of a glass cloth are each formed by combining several hundreds of glass fibers having a diameter of about several micrometers in a parallel fashion. At this time, a sizing agent (also referred to as a binding agent or a size) for binding the glass fibers together is used. The sizing agent binds the glass fibers together. Also, the sizing agent forms a coating on the surfaces of the fibers, thereby protecting the glass yarns during weaving and preventing fuzzing. Therefore, the use of a sizing agent is essential for formation of glass yarns and glass cloths.